Interleukin-6 as A Prognostic Biomarker in Perinatal Asphyxia

Objective Early diagnosis is has a crucial role in both prevention and treatment of asphyxia-related complications. The current study aimed to evaluate the prognostic value of interleukin-6 (IL-6) and hypoxic-ischemic encephalopathy grade in the prediction of mortality and the developmental status of neonates affected by prenatal asphyxia. Materials & Methods This cohort study was conducted on 38 term asphyxiated infants at Ghaem hospital, Mashhad, Iran, from 2013 to 2017. The HIE grade and serum IL-6 levels were determined at the time of birth. The developmental status was evaluated using the Denver II test at the end of the two-year follow-up. Results HIE grade 3 resulted in 83% mortality rate and developmental delay among all survivors. The mean IL-6 level was 2.7 ng/ml in the control group (not affected HIE), which increased up to 29, 175, and 136 ng/ml in those with HIE grades of 1, 2, and 3, respectively. According to the ROC curve analysis, the cut-off level of 24 pg/ml could predict the developmental delay with sensitivity and specificity of 96 and 92%, respectively. Conclusion The IL-6 level and HIE grade are potential prognostic biomarkers for the determination of mortality and morbidity in asphyxiated neonates.


Introduction
Despite advances in perinatal care, asphyxia is a major cause of mortality and permanent neurological as well as developmental complications in neonates (1). According to the World Health Organization (WHO), mild-tosevere asphyxia occurs in 3% (6.3 million cases) of newborns, born in developing countries. It claims 840,000 lives and causes severe consequences in almost all survivors (2). systematic review and meta-analysis. Heliyon, 6(4), e03793. (4) and may have consequences such as cerebral palsy, epilepsy, and learning disabilities (2,5). Therefore, prediction of prognosis of asphyxia is a priority for both prevention and treatment of its complications (6).
Currently, the diagnosis of asphyxia is based on electronic fetal monitoring during labor, presence of meconium in the amniotic fluid, Apgar score, signs of HIE (7,8), and multi-organ disorder within 72 hours after delivery. These clinical symptoms are supplemented with laboratory tests such as measuring fetal scalp blood pH, arterial blood gases testing, nucleated red blood cells, and biochemical markers like lactate, lactate dehydrogenase (LDH), creatine kinase (CK), neuron specific enolase, and several other proteins (9). The role of antioxidant-oxidant balance, heat shock protein, and interleukins (10) in prognosis of asphyxia is evaluated by several studies.
Hence, determining the prognosis of asphyxia is considered a priority for the prevention and treatment of its complications (6). There is no correlation between current diagnostic criteria and patients' prognosis, and in the absence of reliable markers (11), early diagnosis of HIE of asphyxia and its related brain damage is a challenging task in neonatal care (12). Recently, it has been reported that inflammatory cytokines contribute to the pathogenesis of ischemic brain injury (13).
Increased level of IL-1 ß, IL-8, and IL-6 is reported in neonates who suffer from asphyxia (14). It is well-documented that IL-6 concentration in the cerebrospinal fluid (CSF) is associated with severe HIE, brain damage, and neurological outcomes (15). In addition, some studies reported increased levels of IL-6 and tumor necrosis factor-alpha (TNF-α) in the cerebrospinal fluid of infants with HIE (16). While both asphyxia and sepsis cause increased plasma level of IL-6 concentration, TNF-α level is more associated with sepsis (16).
Serum IL-6 level has been reported to increase within the first 24 hours after hypoxic ischemia (16). Therefore, measuring the IL-6 level in the umbilical cord blood and peripheral blood serum has been reported as a relatively simple method to predict brain damage and other adverse consequences caused by asphyxia (3,17). In the present study, serum level of IL-6 and other clinical and laboratory results were evaluated as biomarkers for prognosis of perinatal asphyxia, which is a less invasive approach. Hence, the current study aimed to evaluate the prognostic value of (IL-6) and hypoxic-ischemic encephalopathy (3) grade in the prediction of mortality and developmental status of neonates affected by prenatal asphyxia.

Selection of participants
The study protocol of this observational (prospective cohort) research is approved by the

Correlation between IL-6 Concentration and HIE grade
IL-6 concentration in the asphyxiated neonates with different grades of HIE is shown in Figure   2. According to the findings, the mean level of IL-6 was increased from 2.7 in the control group (not affected HIE) to 29, 175, and 136 ng/ml in those with HIE grades of 1, 2, and 3, respectively.
Hence, HIE grade 1 did not significantly change the IL-6 level ((p> 0.1). It also suggests that IL-6 concentration may reach its maximum in neonates with HIE grade 2. Therefore, there was no significant difference concerning the IL-6 concentration between those with HIE grades of 2 and 3 (p> 0.2).

Correlation between IL-6 Concentration and Developmental Delay
As shown in Figure 3, there was a statistically ROC curve analysis (Fig. 4)

Interleukin-6 as A Prognostic Biomarker in Perinatal Asphyxia
Iran J Child Neurol. Summer 2021 Vol. 15 No. 3

Discussion
To improve the management procedures, many attempts have been made to accurately predict the prognosis of asphyxiated neonates by combining the results of clinical examinations with laboratory  There is a controversy regarding the role of IL-6 in the pathogenesis of brain damages caused by asphyxia. The rise in IL-6 level may support the possible role of this cytokine in the pathogenesis of hypoxic-ischemic brain injury (16). However, it has been suggested that IL-6 might be released as a protective response after hypoxic-ischemic brain injury and is involved in the repair process

In Conclusion
This study revealed more details and suggested cut-offs for HIE grades and IL-6 levels, as potential prognostic biomarkers for mortality and morbidity caused by neonatal asphyxia. When followed for two years, neonatal IL-6 concentrations above 24 nl/L combined with HIE grades of 2 and 3 and acidosis indicated a high mortality rate and developmental delay among survivors. Therefore, these three parameters may have a crucial role in the identification of those asphyxiated neonates who need early intervention to alleviate asphyxiarelated developmental delay. Rakhshanizadeh carried out the initial analyses, reviewed and revised the manuscript, and approved the final manuscript as submitted.

Author's Contribution
Maryam Zakerihamidi designed the data collection instruments, and coordinated and supervised data collection at two of the four sites, critically reviewed the manuscript, and approved the final manuscript as submitted.
All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.